The project is concerned with characterizing and determining the function of a group of RNA molecules and a group of proteins that shuttle non-randomly between nucleus and cytoplasm. The studies assume that this shuttling behavior is related to the control of gene function. These studies will be carried out with free-living amebae with which nuclei can be transferred between specifically labeled and unlabeled cells and with mammalian cells with which nuclei can be "transferred" between specifically labeled and unlabeled cells by means of fusion between nucleate and enucleate cells. The molecules will be characterized by their intracellular localization, their shuttling behavior, their electrophoretic mobilities following extraction, their interaction with other molecules, etc. Their functions will be explored by determining the effects of such altered cellular physiological activities as: (1) cells in log phase vs. cells in stationary phase; (2) contact inhibited cells vs. non-contact inhibited cells; (3) malignant vs. non-malignant cells; (4) cells inhibited from transcribing vs. normally transcribing cells; and (5) cells with "genetically inert" nuclei vs. cells with active nuclei. Their influence on such metabolic activities as DNA replication, transcription, and translation also will be explored. BIBLIOGRAPHIC REFERENCES: Goldstein, L., and C. Ko. 1976. A Method for the Mass Culturing of Large Free-Living Amebae. Methods in Cell Biol., in press. Goldstein, L. 1976. Nucleus, Cytoplasm, and Their Interactions. Proceedings, IX World Congress of Anatomic and Clinical Pathology, in press.